The heavy-mineral assemblages of Pleniglacial fluvial sediments were analysed for two river valleys, viz. the Luciąża River (at Kłudzice Nowe) and the Belnianka River (at Słopiec). These sites, on the Piotrków Plateau and in the Holy Cross Mountains respectively, are located in different morphogenetic zones of Poland that were affected to different degrees by the Middle Polish ice sheets. The study was aimed at determining the kind of processes that modified the heavy-mineral assemblages in the two fluvial sediments, at reconstructing the conditions under which these processes took place, and in how far these processes caused changes in the assemblages. The heavy-mineral associations of the parent material was taken as a starting point; this parent material were the sediments left by the Odranian glaciation (Warta stadial = Late Saalian). It was found that heavy-mineral assemblages in the Luciąża valley deposits are varied, particularly if compared with other fluvioglacial Quaternary deposits from the Polish lowlands, with a dominance of garnet. In the fluvial deposits of the Belnianka valley, zircon, staurolite and tourmaline dominate, with minor amounts of amphibole, pyroxene, biotite and garnet. This suggests that the deposits were subject to intensive and/or persistent chemical weathering and underwent several sedimentation/erosion cycles under periglacial conditions. In both valleys chemical weathering and aeolian processes were the main factors that modified the assemblages of the transparent heavy minerals; these processes were largely controlled by the climatic changes during the Pleistocene.

Terrestrial environments tend to be characterized by an incomplete record of past conditions. For the MIS 3–2 periods, there is only one known site in Poland—Horoszki Duże—in which a probably continuous record of climate change has been preserved. However, this site does not have any high precision multi-proxy analyses. In the absence of continuous high-resolution records, we decided to gather and analyze scattered information. We assembled data originating from various sites in Poland and checked whether the available results of 14C and luminescence dating presented in the form of probability density distributions (PDF) and kernel density estimation (KDE) models would allow their reinterpretation. The data were compared to the Greenland isotope curve to see whether they were consistent with the hypothesis that the number of “warming-cooling” cycles recorded in the examined sediments was of the same order as in those ice-core records. Previously in Poland, usually only two interstadial periods (i.e., Hengelo and Denekamp, 36–38.6 and 28–32 14C kBP, respectively) have been identified in the discussed period. The joint analysis of data from a larger area revealed more warming-cooling events than recorded from individual sites.